Datasheet

LTC3549
7
3549f
PI FU CTIO S
UUU
V
IN
(Pin 1): Main Supply Pin. Must be closely decoupled
to GND, Pins 2 and 7, with a 4.7µF or greater ceramic
capacitor.
GND (Pin 2): N/C. Ground this pin.
SW (Pin 3): Switch Node Connection to Inductor. This pin
connects to the drains of the internal main and synchronous
power MOSFET switches.
MODE (Pin 4): Mode Select Input. To select pulse-skip-
ping mode, force this pin above 1.1V. Forcing this pin
below 0.3V selects Burst Mode operation. Do not leave
MODE fl oating.
RUN (Pin 5): Run Control Input. Forcing this pin above 1.1V
enables the part. Forcing this pin below 0.3V shuts down
the device. In shutdown, all functions are disabled drawing
<1µA supply current. Do not leave RUN fl oating.
V
FB
(Pin 6): Feedback Pin. Receives the feedback voltage
from an external resistive divider across the output.
GND (Pin 7): Exposed Pad. The Exposed Pad is ground. It
must be soldered to PCB ground to provide both electrical
contact and optimum thermal performance.
FU CTIO AL DIAGRA
UU
W
+
–
+
–
+
–
EA
+
–
OVDET
+
–
I
RCMP
+
–
I
COMP
6
5
RUN
SLOPE
COMP
OSC
0.611V
REFERENCE
SHUTDOWN
OV
0.671
0.4V
0.65V
SLEEP
EN
V
IN
V
FB
4
MODE
BURST
V
IN
S
R
RS LATCH
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
ANTI-
SHOOT-
THRU
SOFT-
START
Q
Q
5Ω
1
SW
3
GND
3549 FD
2
GND
7
OSCILLATOR